Method of manufacturing semiconductor devices and semiconductor device containing hydrogen-related donors

ABSTRACT

Crystal lattice defects are generated in a horizontal surface portion of a semiconductor substrate and hydrogen-related donors are formed in the surface portion. Information is obtained about a cumulative dopant concentration of dopants, including the hydrogen-related donors, in the surface portion. Based on the information about the cumulative dopant concentration and a dissociation rate of the hydrogen-related donors, a main temperature profile is determined for dissociating a defined portion of the hydrogen-related donors. The semiconductor substrate is subjected to a main heat treatment applying the main temperature profile to obtain, in the surface portion, a final total dopant concentration deviating from a target dopant concentration by not more than 15%.

BACKGROUND

Power semiconductor devices typically include a low-doped drift zoneacross which the blocking voltage drops. When the drift zone is formedin an epitaxial layer grown on a heavily doped semiconductor base,in-situ doping during the epitaxial growth facilitates a highlyhomogeneous distribution of the dopants within the epitaxial layer.Since the growth rate of epitaxial layers is about 1 μm per minute, theprocess is comparatively expensive for drift zones with a thickness of100 μm and more. Therefore, semiconductor wafers for the manufacture ofsemiconductor devices with high blocking capability are typicallyobtained by sawing from silicon ingots, which grow from a localizedfloating melting zone of a rod from a raw material. During the floatingzone melting process, the growing silicon crystal typically incorporatesdopant atoms at comparatively high homogeneity across the length and thediameter of the silicon ingot but the costs of this process arerelatively high and the maximum available wafer diameter is 12″. Drawinga silicon ingot from molten raw material in a crucible in a Czochralskiprocess, on the other hand, provides silicon ingots with diametersgreater than 12″ in an economic way but at the costs of comparativelyhigh axial inhomogeneity.

It is desirable to improve the manufacture of power semiconductordevices.

SUMMARY

According to an embodiment a method of manufacturing semiconductordevices includes generating crystal lattice defects in a horizontalsurface portion of a semiconductor substrate and forminghydrogen-related donors in the surface portion. Information is obtainedabout a cumulative dopant concentration of dopants, including thehydrogen-related donors, in the surface portion. Based on theinformation about the cumulative dopant concentration and a dissociationrate of the hydrogen-related donors, a main temperature profile isdetermined for dissociating a defined portion of the hydrogen-relateddonors. The semiconductor substrate is subjected to a main heattreatment applying the main temperature profile to obtain, in thesurface portion, a final total dopant concentration deviating from atarget dopant concentration by not more than 15%.

According to another embodiment a semiconductor device includes asemiconductor portion including a drift zone with a total dopantconcentration in a range from 1E12 cm⁻³ to 1E17 cm⁻³, wherein a ratio ofhydrogen-related donors to a total of extrinsic donors is at least 25%and wherein the hydrogen-related donors including oxygen atoms, carbonatoms or both oxygen and carbon atoms, as well as hydrogen-relateddonors containing neither oxygen nor carbon atoms.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification. The drawings illustrate the embodiments ofthe present invention and together with the description serve to explainprinciples of the invention. Other embodiments of the invention andintended advantages will be readily appreciated as they become betterunderstood by reference to the following detailed description.

FIG. 1 is a schematic block diagram for illustrating a method ofmanufacturing a semiconductor device by generating a sufficiently highcumulative dopant concentration and lowering the cumulative dopantconcentration by dissociating excess HDs (hydrogen-related donors) in afeed-forward process.

FIG. 2A is a schematic diagram for illustrating dopant concentrationsand concentration of interstitial oxygen at different process stagesaccording to an embodiment concerning high-resistive semiconductorsubstrates.

FIG. 2B is a schematic diagram for illustrating dopant concentrationsand concentration of interstitial oxygen at different process stagesaccording to an embodiment concerning p-type semiconductor substrates.

FIG. 2C is a schematic diagram for illustrating dopant concentrationsand concentration of interstitial oxygen at different process stagesaccording to an embodiment concerning n-type semiconductor substrates.

FIG. 3A is a schematic vertical cross-sectional view of a portion of asemiconductor substrate for illustrating a method of manufacturingsemiconductor devices including defined dissociation of hydrogen-relateddonors, after forming p-type anode/body wells in device regions.

FIG. 3B is a schematic vertical cross-sectional view of thesemiconductor substrate portion of FIG. 3A, during a first implantgenerating crystal lattice defects in a surface portion.

FIG. 3C is a schematic vertical cross-sectional view of thesemiconductor substrate portion of FIG. 3B, after a preparatory heattreatment for achieving a cumulative dopant concentration containingHDs.

FIG. 3D is a schematic vertical cross-sectional view of thesemiconductor substrate portion of FIG. 3C, during obtaining informationabout the cumulative dopant concentration.

FIG. 3E is a schematic vertical cross-sectional view of thesemiconductor substrate portion of FIG. 3D, after a main heat treatmentdissociating a predetermined amount of hydrogen-related donors.

FIG. 3F is a schematic vertical cross-sectional of the semiconductorsubstrate portion of FIG. 3E, after attaching a carrier member at afront side of the semiconductor substrate.

FIG. 3G is a schematic vertical cross-sectional of the semiconductorsubstrate portion of FIG. 3F, after thinning the semiconductor substratefrom a rear side.

FIG. 3H is a schematic vertical cross-sectional of the semiconductorsubstrate portion of FIG. 3G, during a second implant through the rearside for forming a field stop layer.

FIG. 3I is a schematic vertical cross-sectional of the semiconductorsubstrate portion of FIG. 3H, after a supplementary heat treatmentforming the field stop layer.

FIG. 3J is a schematic vertical cross-sectional of the semiconductorsubstrate portion of FIG. 3I, after forming a rear side metallization.

FIG. 3K is a schematic vertical cross-sectional of semiconductor diesobtained from the semiconductor substrate portion of FIG. 3J byseparation along dicing streets.

FIG. 4 is a schematic diagram illustrating a hydrogen-related donorconcentration in a semiconductor substrate as a function of atemperature of a heat treatment lasting for five hours to discussbackground useful for understanding of the embodiments.

FIG. 5A is a schematic diagram for illustrating a capacitance-voltagemeasurement for determining a cumulative dopant concentration by using acontact probe forming a Schottky contact.

FIG. 5B is a schematic diagram for illustrating a capacitance-voltagemeasurement for determining a cumulative dopant concentration by usingan auxiliary structure in a kerf region.

FIG. 5C is a schematic diagram for illustrating a capacitance-voltagemeasurement for determining a cumulative dopant concentration by using agate electrode.

FIG. 6 includes schematic diagrams for illustrating the impact of oxygenand carbon content in the semiconductor substrate on generation anddissociation rate of hydrogen-related donors.

FIG. 7A is a schematic vertical cross-sectional view of a powersemiconductor device with a drift zone in which HDs represent at least25% of the total dopant concentration according to an embodiment.

FIG. 7B is a schematic diagram illustrating a vertical dopant profilethrough the power semiconductor device of FIG. 7A.

FIG. 8A is a schematic vertical cross-sectional view of a powersemiconductor diode with HDs representing at least 25% of a total dopantconcentration in a drift zone according to an embodiment.

FIG. 8B is a schematic vertical cross-sectional view of an IGFET(insulated gate field effect transistor) with HDs representing at least25% of a total dopant concentration in a drift zone according to afurther embodiment.

FIG. 8C is a schematic vertical cross-sectional view of an IGBT(insulated gate bipolar transistor) with HDs representing at least 25%of a total dopant concentration in a drift zone according to anotherembodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof and in which are shownby way of illustrations specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations. The examples are described using specific language, whichshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only.Corresponding elements are designated by the same reference signs in thedifferent drawings if not stated otherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open, and the terms indicate the presence of stated structures,elements or features but do not preclude additional elements orfeatures. The articles “a”, “an” and “the” are intended to include theplural as well as the singular, unless the context clearly indicatesotherwise.

The term “electrically connected” describes a permanent low-ohmicconnection between electrically connected elements, for example a directcontact between the concerned elements or a low-ohmic connection via ametal and/or highly doped semiconductor. The term “electrically coupled”includes that one or more intervening element(s) adapted for signaltransmission may be provided between the electrically coupled elements,for example elements that are controllable to temporarily provide alow-ohmic connection in a first state and a high-ohmic electricdecoupling in a second state.

The Figures illustrate relative doping concentrations by indicating “−”or “+” next to the doping type “n” or “p”. For example, “n−” means adoping concentration which is lower than the doping concentration of an“n”-doping region while an “n+”-doping region has a higher dopingconcentration than an “n”-doping region. Doping regions of the samerelative doping concentration do not necessarily have the same absolutedoping concentration. For example, two different “n”-doping regions mayhave the same or different absolute doping concentrations.

FIG. 1 shows a semiconductor substrate 100 at different stages ofprocessing. The material of the semiconductor substrate 100 is acrystalline semiconductor material, for example silicon (Si), siliconcarbide (SiC), germanium (Ge), silicon germanium (SiGe), gallium nitride(GaN), gallium arsenide (GaAs) or any other A_(III)B_(V) semiconductor.The semiconductor substrate 100 may be a single-crystalline siliconwafer with a planar front surface 101 and a supporting surface 102 onthe back opposite to the front surface 101, e.g., from monocrystallineCzochralski silicon (Cz:Si) obtained by sawing from a cylindricalsilicon ingot extracted from a silicon melt in a crucible in aCzochralski process in the absence of magnetic fields, magneticCzochralski silicon (mCz:Si) obtained by applying a strong magneticfield controlling the convection flow in the silicon melt duringextraction of the silicon ingot from the silicon melt, or floating zonesilicon (Fz:Si) obtained from a silicon ingot extracted from a meltingzone of a rod from a non-single crystalline raw material.

Shape, dimensions and material of the semiconductor substrate 100 arecompatible with production lines for silicon-based semiconductordevices. For example, the semiconductor substrate 100 may be a siliconwafer with an approximately cylindrical shape, wherein the diameter ofthe silicon wafer may be at least 150 mm, e.g., 200 mm (“8 inch”), 300mm (“12 inch”), or 450 mm (“18 inch”). A thickness of the semiconductorsubstrate 100 may be between 100 μm and several millimeters, e.g., in arange from 500 μm to 2 mm, by way of example. A normal to the frontsurface 101 defines a vertical direction. Directions parallel to thefront surface 101 are horizontal directions.

The semiconductor substrate 100 is subjected to processes for formingelectronic elements in and on the semiconductor substrate 100. At asuitable stage of processing, a sequence of processes generates HDs(hydrogen-related donors) in at least a horizontal surface portion ofthe semiconductor substrate 100, which extends along and parallel to thefront surface 101.

The process of generating HDs may start with the generation of crystallattice defects at least in the surface portion of the semiconductorsubstrate 100, wherein the surface portion directly adjoins to the frontsurface 101. For example, an implantation apparatus 410 irradiates thefront surface 101 with a particle beam 412 containing particles, e.g.,electrons, neutrons, protons or helium ions. The particles enter thesemiconductor substrate 100 through the front surface 101, traverse thesurface portion and come to rest around an end-of-range peak in thesemiconductor substrate 100, wherein inter alia mass and energy of theparticles define a distance of the end-of-range peak to the frontsurface 101.

In the surface portion the traversing particles generate intrinsic pointdefect complexes, for example vacancy or multi-vacancy complexes,wherein a mean defect density Ndd in the area of the end-of-range peakmay be in range from 1E17 cm-3 to 1E20 cm-3 and a mean defect densityNdd in the traversed surface portion between the front surface 101 andthe end-of-range peak is approximately 10% of the mean defect densityNdd in the area of the end-of-range peak. Then a preparatory heattreatment diffuses hydrogen into the traversed surface portion. In casethe particle beam 412 contains a sufficient number of protons, thesemiconductor substrate 100 may be directly transferred to a firstheating chamber 420 that subjects the semiconductor substrate 100 to thepreparatory heat treatment in course of which the implanted hydrogendiffuses from the region around the end-of-range peak into both verticaldirections.

Hydrogen atoms diffusing through an unaffected base portion of thesemiconductor substrate 100 between the end-of-range peak and thesupporting surface 102 remain electrically inactive and have not furtherimpact on the dopant concentration in the semiconductor substrate 100.

In the surface portion between the front surface 101 and theend-of-range peak, the crystal lattice defects getter hydrogen atoms andtransform into electrically active defect complexes containing hydrogen,i.e., hydrogen-related donors (HDs).

In case the hydrogen content in the semiconductor substrate 100 is notsufficient, for example, in case the particle beam 412 contains otherparticles than protons for the creation of vacancies, formation of thehydrogen-related donors may further include in-diffusion from a hydrogenplasma source before the preparatory heat treatment.

The preparatory heat treatment applies a preparatory temperature profileTproc1(t), e.g., an isothermal process with a preparatory processtemperature T1 above 300° C. and below 600° C. for a preparatory processtime t1 of at least several hours. According to an embodiment thepreparatory process temperature T1 of an isothermal preparatory heattreatment is in a range from 450° C. to 550° C., e.g., in a range from470° C. to 510° C. and lasts for at least 1 h, at least 2 h, or at least5 h such that the available hydrogen atoms occupy all available crystallattice defects in the surface portion. Since formation of HDs is tiedto the presence of suitable lattice defects, no more HDs can form onceall suitable lattice defects are occupied. In this way a stablepreparatory HD concentration Nhd1 can be achieved, which does notfurther increase as long as no further crystal defects are generated andwhich does not decrease as long as the applied temperature does notexceed the dissociation temperature of the HDs.

After the preparatory heat treatment, information as regards acumulative dopant concentration Ncum in the surface portion is obtained.The cumulative dopant concentration Ncum is a total net dopantconcentration of all electrical active dopants after the preparatoryheat treatment and includes at least the preparatory HD concentrationNhd1 after the preparatory heat treatment. In case the initialsemiconductor material of the semiconductor substrate 100 is highlyresistive, the cumulative dopant concentration Ncum is equal to orclosely approximates the preparatory HD concentration Nhd1. In case theinitial semiconductor material contains extrinsic dopant atoms such as,e.g., arsenic (As), boron (B), and/or phosphorus (P) atoms, thecumulative dopant concentration Ncum is the sum of the preparatoryhydrogen-related donor concentration Nhd1 and the extrinsic dopantconcentration Next, wherein the extrinsic dopant concentration Next isthe net dopant concentration resulting from the total content of donorand acceptor atoms. According to an embodiment, the extrinsic dopantconcentration Next may be in a range from 0 to 1E14 cm⁻³, e.g., from 0to 5E12 cm⁻³.

The preparatory HD concentration Nhd1 results from the density ofcrystal lattice defects in the surface portion, the content of hydrogenin the semiconductor substrate 100 after the irradiation process, thecontent of interstitial oxygen and carbon dissolved in the siliconcrystal as well as the temperature profile applied during thepreparatory heat treatment. The parameters of the process for generatingcrystal lattice defects, the hydrogen content and the temperatureprofile of the preparatory heat treatment may be selected such that (i)the preparatory heat treatment saturates the crystal lattice defectssuitable for formation of HDs, (ii) the HDs are thermally stable in arange between 400° C. and 480° C., and (iii) Ncum exceeds a targetdopant concentration Ntar by at least 5%, e.g., by at least 20%.

From the cumulative dopant concentration Ncum a control unit 490determines a main temperature profile Tproc2(t) for a main heattreatment that reduces the number of hydrogen-related donors such that afinal total dopant concentration Ntot fulfills a predeterminedcondition, e.g., deviates by not more than 15%, by not more than 10% orby not more than 5% from the target dopant concentration Ntar.

The final total dopant concentration Ntot is a total net dopantconcentration of all electrical active dopants after the main heattreatment and includes at least the final HD concentration Nhd2 afterthe main heat treatment. In case the initial semiconductor material ofthe semiconductor substrate 100 is highly resistive, the final totaldopant concentration Ntot is equal to or closely approximates the finalHD concentration Nhd2. In case the initial semiconductor materialcontains extrinsic dopant atoms the final total dopant concentrationNtot is the sum of the final HD concentration Nhd2 and the extrinsicdopant concentration Next.

The main temperature profile Tproc2(t) may be an isothermal profiledefined by a constant main process temperature Tproc2, a main processtime tproc2 during which the main process temperature Tproc2 is appliedas well as falling and trailing temperature ramps before and afterapplying Tproc2.

The control unit 490 determines the main temperature profile Tproc2(t)by considering the HD dissociation rate in the semiconductor substrate100. The minimum main process temperature Tproc2 for dissociating theHDs is higher than the preparatory process temperature Tproc1, e.g.,above 380° C. or, in case Tproc1 exceeds 380° C., above 480° C.

The semiconductor substrate 100 may be subjected to the main heattreatment in a second heating chamber 470 at any later stage ofprocessing after obtaining the information on the cumulative dopantconcentration Ncum and before the semiconductor substrate 100 isseparated into a plurality of identical semiconductor dies. According toan embodiment, the main heat treatment is performed before forming ametallization on the front surface 101. The main heat treatment may be adedicated heat treatment exclusively serving for dissociating a desirednumber of HDs.

With the method of FIG. 1 a simple feed-forward control either achievesa well-defined low-doped surface portion in a high-resistivesemiconductor substrate 100 or completes an original background dopantconcentration in a comparatively low-resistive semiconductor substrate100 to a desired target donor concentration by filling a gap between thetarget dopant concentration Ntar and the extrinsic dopant concentrationNext with HDs.

Compared to other approaches including feed-forward control, forexample, by filling the gap between the target dopant concentration Ntarand an extrinsic dopant concentration Next with a defined generation ofOTDs (oxygen-related thermal donors), the present embodiment gets alongwithout knowledge of the exact content of interstitial oxygen andcarbon. Instead, the method makes use of the observation that, otherthan a generation rate, a total dissociation rate of HDs does not dependor depends only to a negligible degree on the presence of otherimpurities, e.g., interstitial oxygen and carbon atoms, at least in arange of interest. The range of interest includes the typicalspecification ranges for interstitial oxygen and carbon impurities inmCz:Si and a target dopant concentration Ntar below 3E15 cm-3.

For example, interstitial oxygen in combination with hydrogen formshydrogen-related donor complexes that differ from other oxygen-freehydrogen-related donor complexes. But at temperatures above 460° C. thehydrogen-related donors with and without oxygen-related donors such asODTs dissociate at almost equal rates.

As a consequence the method can get along without knowledge of the exactoxygen content and it is sufficient that the semiconductor substrate 100fulfills the usual tolerance conditions as regards oxygen content andcarbon content.

FIGS. 2A and 2C show pertinent dopant concentrations and theconcentration of interstitial oxygen at different stages of processingfor different types of the semiconductor substrates 100.

FIG. 2A concerns a high-resistive semiconductor substrate that containsextrinsic dopant atoms only as unwanted impurities with a concentrationlower than 1E12 cm⁻³.

Diagram 901 refers to a high-resistive semiconductor substrate beforethe formation of HDs. The intrinsic oxygen concentration is within aspecified range between a minimum intrinsic oxygen concentration NiO1and a maximum intrinsic oxygen concentration NiO2. A concentration ofsubstitutional carbon is within a specified range between a minimumconcentration of substitutional carbon NsC1 and a maximum concentrationof substitutional carbon NsC2.

Knowledge about the tolerance ranges ΔNiO=|NiO1−NiO2| andΔNsC=|NsC1−NsC2| suffices to determine parameters of a process forforming HDs, for example, the dose of a proton implant and a temperatureprofile in a preparatory heat treatment for diffusing the protons toachieve, by generating HDs, a cumulative dopant concentration Ncum,which is safely greater than the target dopant concentration Ntar.

Diagram 902 shows the cumulative dopant concentration Ncum, which is atleast 5%, e.g., at least 20% higher than the target dopant concentrationNtar. The cumulative dopant concentration Ncum is equal to a preparatoryHD concentration Nhd1 that includes hydrogen-related donors both withand without oxygen and/or carbon atoms.

Irrespective of the oxygen content, the carbon content, the content ofoxygen-related dopants and/or the content of carbon-related dopants, atleast for a range of interest with Ncum lower than 3E15 cm-3 the totaldissociation rate of hydrogen-related donors can be considered to be thesame and knowledge about Ncum is sufficient to define a main temperatureprofile that reduces Ncum to a value Ntot, which deviates from thetarget dopant concentration Ntar by not more than 15%, e.g., by not morethan 10% or by not more than 5% as illustrated in diagram 903.

FIG. 2B refers to an n-doped semiconductor substrate with an initialextrinsic donor concentration N_(D) of donors, for example, arsenicand/or phosphorus atoms within a specified range between a minimumexternal dopant concentration Next1 and maximum external dopantconcentration Next2, with Next2 lower than Ntar as shown in diagram 911.

Knowledge about the tolerance ranges ΔNiO and/or ΔNsC as well as ΔNextmay suffice to determine parameters of a process for forming HDs, forexample, by implanting and diffusing protons to achieve, after theformation of HDs in a preparatory heat treatment between, e.g., 470° C.and 510° C., a cumulative dopant concentration Ncum, which is the sum ofthe external dopant concentration Next and the preparatory HDconcentration Nhd1, to be safely greater than the target dopantconcentration Ntar as shown in diagram 912.

The following main heat treatment reduces Ncum to Ntar as illustrated indiagram 913.

Determining the temperature profile of the main heat treatment may getalong with the knowledge of only the cumulated dopant concentration Ncumand the dissociation rate provided that the absolute variation of theexternal dopant concentration is sufficiently low.

Otherwise, i.e., if the fluctuation of external dopant concentration hassignificant impact on the final total dopant concentration Ntot, theprocess for determining the process parameters may include a furtherprocess for obtaining information about the actual extrinsic dopantconcentration Next in the concerned semiconductor substrate. Forexample, a spreading resistance measurement may determine the extrinsicdopant concentration at an early stage of processing before forming thehydrogen-related dopants.

According to another embodiment, a first partial heat treatment for thedissociation process ends after a defined first dissociation time andinformation descriptive for a reduced cumulated dopant concentrationNredcum is obtained in the same way as for the cumulated dopantconcentration Ncum to determine, from the first dissociation time andthe difference between Ncum and Nredcum, the ratio of HDs to extrinsicdopants in the cumulated dopant concentration Ncum. The parameters ofthe process for generating crystal lattice defects, the hydrogen contentand the temperature profile of the preparatory heat treatment and thefirst partial heat treatment for the dissociation process are selectedsuch that the reduced cumulated dopant concentration Nredcum exceeds atarget dopant concentration Ntar by at least 5%, e.g., by at least 20%.Then a second dissociation time for a second partial heat treatment ofthe dissociation process can be tuned to the calculated ratio of HDs toextrinsic dopants.

In FIG. 2C the diagrams 921-923 correspond to the diagrams 911-913 incase the semiconductor substrate is p-type and the extrinsic dopantconcentration Next is an acceptor concentration N_(A).

FIGS. 3A to 3K concern the manufacture of a plurality of semiconductordies from a common semiconductor substrate 100, wherein formation ofhydrogen-related donors includes implantation of protons.

Semiconducting regions, for example, anode layers of a semiconductordiode or body and source regions of transistor cells are formed at afront side of a semiconductor substrate 100 in device regions 610.Further, insulating and conductive structures, for example, planar gatestructures or trench gate structures, field plate structures andtermination structures may be formed within each device region 610.

The semiconductor substrate 100 shown in FIG. 3A may be intrinsic, ormay contain extrinsic dopants, such as boron, phosphorus, arsenic,antimony and contaminants such as interstitial oxygen and substitutionalcarbon atoms. The device regions 610 form a matrix with lines andcolumns, wherein a kerf region 690 separates neighboring device regions610 from each other. The kerf region 690 forms a grid, wherein each meshof the grid includes one device region 610.

FIG. 3A shows p-type anode/body wells 120 as a pars-pro-toto example ofa semiconducting structure for a device region 610, wherein theanode/body well 120 may be the anode layer of a power semiconductordiode or the body well of a transistor cell array that further includesn-type source regions between the front surface 101 and the anode/bodywells 120.

Formation of the anode/body wells 120 and further semiconducting regionsmay include implanting the dopants into the semiconductor substrate 100,annealing the crystal damage and integrating the implanted dopant atomsat regular crystal lattice sites as well as diffusing the implanteddopant atoms at temperatures above 800° C.

After finalization of the semiconducting regions such as the anode/bodywells 120, e.g., after annealing and diffusing, a particle implantgenerates crystal lattice defects, for example, point defects ormulti-point defects in a surface portion 110 that directly adjoins thefront surface 101. The particle implant may be performed after formationof the gate dielectric.

FIG. 3B shows a particle beam 412 directed to the front surface 101. Theparticle beam 412 may impinge orthogonal to the front surface 101 toexploit channeling effects for increasing the implant depth. Accordingto an embodiment, an implant angle between the normal to the frontsurface 101 and the particle beam 412 is in a range from 3° to 10° toavoid channeling effects.

The particles in the particle beam 412 may be electrons, neutrons orhelium ions. According to an embodiment, the particles are protons. Theimplanted particles come to rest at a projected range defined, e.g., bythe energy of the particles, the mass of the particles, and substratecharacteristics. In the surface portion 110 the particles generatecrystal lattice defects, for example, point defects. A first verticalextension v1 of the surface portion 110 is defined by the distance ofthe projected range of the implanted particles from the front surface101. A base portion 190 of the semiconductor substrate 100 between thesurface portion 110 and a supporting surface 102 opposite to the frontsurface 101 remains widely unaffected and does not show any significantincrease of crystal lattice defects.

Irradiation with the particle beam 412 may be performed after finalizingthe anode/body wells 120 and further semiconducting elements.

A preparatory heat treatment is applied to the semiconductor substrate100. The preparatory heat treatment may directly follow the irradiationwith the particle beam 412 of FIG. 3B provided that the particles areprotons. Otherwise a step of supplying hydrogen to the semiconductorsubstrate 100 precedes the preparatory heat treatment.

The preparatory heat treatment may be a dedicated heat treatment servingno other purpose than forming HDs in the surface portion 110. Accordingto other embodiments the preparatory heat treatment may be a heattreatment serving also a further purpose in the course of processingsemiconductor elements in the device regions 610.

During the preparatory heat treatment the maximum temperature applied tothe semiconductor substrate 100 is above 450° C. and at most 550° C.such that HDs of a species of lower thermal stability (HD1) dissociateand exclusively HDs of a species of higher thermal stability (HD2) areformed. The preparatory heat treatment diffuses the hydrogen, whereinthe diffusion length achieved by the preparatory heat treatment is atleast equal to the first vertical extension v1 of the surface portion110. In the surface portion 110, which contains the previously formedcrystal lattice defects, the hydrogen atoms decorate the point defectcomplexes and form donor-like defect states, which are stationary andthermal stable up to about 500° C.

According to FIG. 3C, the surface portion 110 becomes n-type and formsfirst pn junctions pn1 with the anode/body wells 120. Formation of thehydrogen-related donors may include the formation of OTDs, wherein thefinal concentration of OTDs in the surface portion 110 depends on theinitial content of interstitial oxygen. The concentration of HDs mayfurther depend on the content of other impurities, such as carbon.

In the surface portion 110 the cumulative dopant concentration Ncum isthe sum of the current preparatory HD concentration Nhd1 of all types ofHDs after the preparatory heat treatment and an extrinsic dopantconcentration Next. The parameters of the HD generation process, forexample, proton implant dose and temperature as well as duration of thepreparatory heat treatment are selected such that the cumulative dopantconcentration Ncum is greater than a target dopant concentration Ntar ofthe surface portion 110. For example, the cumulative dopantconcentration Ncum is at least 10% or at least 20% higher than thetarget dopant concentration Ntar. The selection of the parameters ofhydrogen implant and preparatory heat treatment may be selected suchthat for a given generation rate of HDs, the specification for thecumulative dopant concentration Ncum is fulfilled even for asemiconductor substrate 100 with the minimum specified content ofinterstitial oxygen, the minimum content of substitutional carbon, andwith either the minimum specified content of extrinsic donors or themaximum concentration of extrinsic acceptors.

At any later process stage after the preparatory heat treatment butbefore any process applying temperatures above the dissociationtemperature of the thermally more stable HD species (HD2), informationabout the cumulative dopant concentration Ncum is obtained from thesemiconductor substrate 100. The measurement concerning the cumulativedopant concentration Ncum may be carried out before applying any furthersignificant thermal budget to the semiconductor substrate 100 after thepreparatory heat treatment.

The measurement may include capacitance-voltage profiling across adepletion zone formed at least in parts in the surface portion 110.

For example, a voltage is applied across a pn junction in thesemiconductor substrate 100 and a capacitance across the pn junction ismeasured as a function of the applied voltage, wherein the capacitanceof the pn junction is a function of the width of the depletion zone.From the dependence of the depletion width upon the applied voltage,information on the dopant concentration in the surface portion 110 canbe obtained.

FIG. 3D shows a measurement unit 820 temporally connected throughcontact probes to the n-type surface portion 110 and to the p-typeanode/body well 120. According to other embodiments, dedicated pnregions may be formed in the device regions 610 or in the kerf region690. Based on a known dissociation rate of HDs and on knowledge upon thecumulative dopant concentration Ncum a main temperature profileTproc2(t) for a main heat treatment may be determined that dissociatesexcess HDs such that the remaining HDs and the extrinsic dopantconcentration supplements to a final total dopant concentration Ntotthat deviates from the target dopant concentration Ntar by not more than15%.

FIG. 3E shows the semiconductor substrate 100 after the semiconductorsubstrate 100 is subjected to the main heat treatment applying the maintemperature profile Tproc2(t). The process exploits the fact that thesame dissociation rate can be assumed for HDs both in the presence ofmore oxygen and/or carbon and in the presence of less oxygen and/orcarbon. As a consequence, the process can get along without knowledge ofthe exact original oxygen content of the semiconductor substrate 100.Provided that the deviation of the extrinsic dopant concentration from amean value is sufficiently low and in case the overall extrinsic dopantconcentration is at most 10% of the target dopant concentration Ntar,the process also gets along without knowledge of the exact extrinsicdopant concentration.

In case a variation of the extrinsic dopant concentration iscomparatively high and the portion of the extrinsic dopant concentrationNext exceeds 10% of the target concentration Ntar, the main heattreatment may be split up into a first partial heat treatment thatcloses only a portion of the gap between the cumulated dopantconcentration Ncum and the target dopant concentration Ntar, forexample, by 50% to achieve a reduced cumulative dopant concentrationNredcum.

The first partial heat treatment may be a dedicated heat treatmentserving no other purpose than dissociating a certain portion of the HDs.Alternatively, the first partial heat treatment applies a definedthermal budget in the course of another process, e.g., during adeposition, reflow, annealing or etching process.

The reduced cumulative dopant concentration Nredcum may be measured inthe same way as Ncum. From the reduced cumulative dopant concentrationNredcum, the cumulative dopant concentration Ncum and the knowndissociation rate of HDs, exact information of the external dopantconcentration Next can be obtained. A second partial heat treatmentdecreasing the reduced cumulative dopant concentration Nredcum to Ntottakes into account the additional information about the external dopantconcentration Next such that a closer agreement of the final totaldopant concentration Ntot with the target dopant concentration Ntar canbe achieved even at comparative high fluctuations of the external dopantconcentration Next.

Alternatively, information about the extrinsic dopant concentration maybe obtained, e.g., by a spreading resistance measurement at an earlyprocess stage before forming any doped regions.

Processing of the semiconductor substrate 100 may proceed withfinalizing semiconducting, insulating and conductive structures in thesemiconductor substrate 100, as well as forming an interlayer dielectricand a first metallization 360 partially separated from the semiconductorsubstrate 100 by the interlayer dielectric on the front side of thesemiconductor substrate 100. A stiff carrier member 810, e.g., agrinding tape, may be reversibly attached at the front side of thesemiconductor substrate 100, for example, by adhesion on the firstmetallization 360.

FIG. 3F shows separated portions of the first metallization 360 for eachdevice region 610. The carrier member 810 may include a rigid,non-stretching film, for example, a temporary bonding adhesive tapeincluding a PET/LCP (polyethylenterephthalat/liquid crystal polymer)base film 812 and a radiation/thermal release adhesive film 811 forreversibly adhering the base film 812 to the first metallization 360.

At least the unaffected base portion 190 of the semiconductor substrate100 may be removed. In addition, at least a section of the surfaceportion 110 including the end-of-range peaks of the particle beam 412 ofFIG. 3B may be removed. For example, a grinding process starting fromthe back of the semiconductor substrate 100 opposite to the carriermember 810 may remove the base portion 190, wherein a grinding wheel maygrind the semiconductor substrate 100 from the supporting surface 102.The grinding process may stop after detection of the doped surfaceportion 110.

FIG. 3G shows the surface portion 110 exposed by removal of the baseportion 190 of FIG. 3F along a grinded surface 103 of the semiconductorsubstrate 100.

FIG. 3H shows rear side processing including formation of a field stoplayer 170 may be applied to the grinded surface 103. According to anembodiment, an implant beam 414 introduces hydrogen through the grindedsurface 103, wherein crystal lattice defects are generated in a rearside surface section with a vertical extension of some ten micrometers.A supplementary heat treatment at a temperature below the dissociationtemperature of the thermally more stable HD species (HD2) diffuses theimplanted hydrogen. Hydrogen atoms diffusing into the rear side surfacesection are gettered at the crystal lattice defects generated by theimplant beam 414 and form a doped field stop layer 170. By contrast,hydrogen atoms diffusing into the surface portion 110 are not gettered,because all previously formed crystal lattice defects in the surfaceportion 110 are saturated by the preceding main heat treatment.

FIG. 3I shows the field stop layer 170 formed between the surfaceportion 110 and the grinded surface 103. Alternatively, the section ofthe surface portion 110 including the end-of-range peak may be used asthe field stop layer 170.

Further rear side processing may define a heavily doped contact layer,e.g., by implanting extrinsic dopant atoms through the exposed grindedsurface 103 and may form a second metallization 370 on the exposedgrinded surface 103.

FIG. 3J shows the thinned semiconductor substrate 100 including thesurface portion 110 containing the anode/body wells 120, the heavilydoped contact layer 180 along the grinded surface 103 and the field stoplayer 170 sandwiched between the surface portion 110 and the contactlayer 180. The contact layer 180 may be n-type for the processing ofn-IGFETs and semiconductor diodes and may be p-type for n-IGBTs. Thesecond metallization 370 may be a continuous layer or may be patternedsuch that separated portions of the second metallization 370 are formedfor each device region 610. A dicing process separates the deviceregions 610 along the kerf region 690.

FIG. 3K shows a plurality of semiconductor dies 590 obtained by dicingalong dicing streets 699 in the kerf region 690 of FIG. 3J, wherein asemiconductor portion 700 with a first surface 701 at a front side and aplanar second surface 702 parallel to the first surface 701 on the backresults from the semiconductor substrate 100 of FIG. 3J. Thesemiconductor portion 700 includes an anode/body well 720 electricallyconnected to a first metallization 360 at the front side and may form apn-junction with a drift zone 731. The drift zone 731 results from thesurface portion 110 of FIG. 3J and a drift zone dopant concentrationNdrift in the drift zone 731 is equal to Ntot. A field stop zone 738results from the field stop layer 170 and a contact zone 739 from thecontact layer 180 of the semiconductor substrate 500 of FIG. 3J.

FIG. 4 schematically shows the content of HDs in a semiconductorsubstrate as a function of a temperature of an isothermal heat treatmentlasting for five hours. Profile 950 shows the total concentration N_(HD)of HDs that has a first plateau for temperatures below about 350° C., afirst significant drop between 350° and 420° C., a second plateaubetween 420° and 480° C. and a final drop starting at about 480° C. Theprofile 950 can be modeled by assuming the existence of two species ofHDs that differ as regards temperature stability. A less stable firstspecies of HDs (HD1) is stable up to temperatures of 380° C. andcompletely dissociates at about 420° C. as illustrated with profile 951.A more stable second species of HDs (HD2) is stable up to temperaturesof 480° C. as illustrated with profile 952. The embodiments use thedifferent temperature stability of HD1 and HD2 to form two differentdoped regions of HD1 and HD2 without the need of mutual adjustment ofthe thermal budgets for the two different doped regions.

FIGS. 5A to 5C refer to methods of obtaining information about thecumulative dopant concentration Ncum after a preparatory heat treatment.The cumulative dopant concentration Ncum may be evaluated at a processstage without ohmic contact at a rear side, at a process stage with atemporary ohmic contact structure, e.g., heavily doped polysilicon atthe rear sides, or with a final rear side contact structure.

FIG. 5A shows a measurement arrangement for CV profiling across aSchottky contact 840 formed by a first contact probe 841 pressed againsta section of the front surface 101 exposing the surface portion 110 inany of the device regions 610 or in the kerf region 690 where acomparatively wide portion of the surface portion 110 is exposed. Ann-type contact region 863 may provide an ohmic transition between thesurface portion 110 and a reference probe 849.

FIG. 5B shows an auxiliary structure 860 completely formed in a kerfregion 690. The auxiliary structure 860 includes a p-type well 861 thatmay be formed contemporaneously with the anode/body wells 120 in thedevice regions 610 of FIG. 3A, a heavily doped p-type contact region 862that may be contemporaneously formed with p-type contact regions in thedevice regions 610 and a heavily doped n-type contact region 863 thatmay be contemporaneously formed with source regions in the deviceregions 610. A portion of the surface portion 110 separates the p-typewell 861 from the n-type contact region 863 such that a second contactprobe 842 in contact with the p-type contact region 862 and a referenceprobe 849 in contact with n-type contact region 863 facilitate a CVprofiling of the pn junction between the surface portion 110 and thep-type well 861.

A CV profiling measures the characteristics of the depletion zone formedalong the pn junction between the p-type well 861 and the surfaceportion 110 in the kerf region 690.

In FIG. 5C a direct contact to a gate electrode 750 replaces the firstcontact probe 841 of FIG. 5A and allows a CV profiling across a gatedielectric 751 separating the gate electrode 750 from a drift zone 731formed from a portion of the surface portion 110. The weakly doped driftzone 731 forms a pn junction with an anode/body well 720 that separatesthe drift zone 731 from a source zone 710.

Information about the cumulative dopant concentration Ncum after thepreparatory heat treatment may also be obtained from a breakdownmeasurement at a conventional test facility for breakdown tests. Thebreakdown measurement typically uses the metallization at the front sideand at the rear side. In case the metallization is not stable at thetypical main process temperature Tproc2 for dissociating the HDs, e.g.,in case the metallization contains aluminum Al as an alloy constituent,the metallization is removed before the main heat treatment.Alternatively, a thermally more stable metallization without aluminum isprovided or a sacrificial conductive layer from, e.g., heavily dopedpolycrystalline silicon is formed for the purpose of the breakdownmeasurement and replaced or covered with a final metallization after themain heat treatment.

FIG. 6 is a combined diagram plotting the integrated active doping of afield stop as a function of different parameters.

Diagram 961 shows that the portion of activated HDs increases withincreasing carbon concentration NsC. Diagram 962 shows the same effectfor increasing oxygen concentration NiO. According to diagrams 963, 964the impact of variations of the carbon concentration and the oxygencontent NsC, NiO decreases with increasing dose of a hydrogen implantfor forming the surface portion and with increasing temperature of themain heat treatment.

FIG. 7A illustrates a power semiconductor device 500 obtained from oneof the above described methods. A single crystalline semiconductormaterial, e.g. silicon, forms a semiconductor portion 700 with a planarfirst surface 701 at a front side as well as a planar second surface 702parallel to the first surface 701 on the back opposite to the frontside.

A minimum distance between the first and second surfaces 701, 702depends on the voltage blocking capability of the power semiconductordevice 500. For example, the distance between the first and secondsurfaces 701, 702 may be in a range from 90 μm to 200 μm in case thepower semiconductor device 500 is specified for a blocking voltage ofabout 1200 V. Other embodiments related to power semiconductor deviceswith higher blocking capabilities may provide semiconductor portions 700with a thickness up to several 100 μm.

In a plane parallel to the first surface 701 the semiconductor portion700 may have a rectangular shape with an edge length in the range ofseveral millimeters or a circular shape with a diameter of severalcentimeters. Directions parallel to the first surface 701 are horizontaldirections and directions perpendicular to the first surface 701 arevertical directions.

The semiconductor portion 700 includes an anode/body well 720electrically connected to a first load terminal L1. A heavily dopedcontact layer 739 is formed along the second surface 702 and iselectrically connected to a second load terminal L2.

A weakly doped drift zone 731 forms one or more pn junctions pn1 withthe anode/body well 720. An effective dopant concentration in the driftzone 731 may be at least 1E12 cm⁻³ and at most 1E17 cm⁻³, typically inthe range between 1E13 cm⁻³ and 1E15 cm⁻³. The doping in the drift zone731 may correspond to an initial background doping in the semiconductorportion 700. At least 25%, e.g., at least 50% of the donors in the driftzone 731 are HDs, wherein the HDs contain a first type of HDs containingoxygen atoms, carbon atoms or both oxygen and carbon atoms and a secondtype of HDs that does not contain neither oxygen nor carbon. The furtherdonors in the drift zone 731 may be hydrogen-related donors or extrinsicdopant atoms such as arsenic, antimony and/or phosphorus atoms.

A field stop zone 738 may separate the contact zone 739 and the driftzone 731 and forms either a unipolar junction or a pn junction with thecontact zone 739 and a unipolar junction with the drift zone 731. Thefield stop zone 738 may contain HDs based on an implant of light ions,e.g., protons and/or extrinsic dopant atoms such as phosphorus, boron,antimony and/or arsenic atoms.

FIG. 7B shows a vertical dopant profile 971 along line B-B of FIG. 7A.The contact zone 739 may be n-doped or p-doped or may include zones ofboth conductivity types. The dopant concentration in the contact zone739 along the second surface 702 is sufficiently high to form an ohmiccontact with a load electrode directly adjoining the second surface 702.For example, an n-doped contact zone 739 may have a mean net dopantconcentration in a range from 1E18 cm⁻³ to 1E20 cm⁻³, for example from5E18 cm⁻³ to 5E19 cm⁻³. The predominant dopants in the contact zone 739may be extrinsic dopant atoms such as boron (B) atoms, arsenic (As)atoms, antimony (Sb) atoms or phosphorus (P) atoms.

In the field stop zone 738 the mean net dopant concentration is at most10% of the maximum dopant concentration in the contact zone 739. Forexample, the mean dopant concentration in the field stop zone 738 may bein a range from 1E14 cm⁻³ to 1E17 cm⁻³, for example from 1E15 cm⁻³ to5E16 cm⁻³, by way of example. The vertical extension of the field stopzone 738 may be in a range from 1 μm to 20 μm, for example from 2 μm to10 μm. The predominant dopants in the field stop zone 738 may beextrinsic dopants or HDs, e.g., HDs of the HD1 species.

In the drift zone 731 the mean net dopant concentration is in a rangefrom 1E12 cm⁻³ to 1E17 cm⁻³, for example, in a range from 3E12 to 5E15or from 1E14 cm⁻³ to 5E15 cm⁻³ and the ratio of HDs to other dopants isat least 25%, e.g., at least 50%, wherein the HDs include HDs withoxygen and/or carbon and HDs with neither oxygen nor carbon. The HDs maybe HDs of the HD2 species. The further dopants in the drift zone 731 maybe extrinsic dopants. The vertical dopant profile 971 may show stepsalong the transitions between the contact zone 739 and the field stopzone 738 as well as between the field stop zone 738 and the drift zone731.

The field stop zone 738 avoids that the depletion zone and the electricfield in the gradually expanding depletion zone reach an electrode atd=0 at the rear side or a backside emitter. When the electric fieldexpands into the direction of the rear side, the power semiconductordevice 500 can continuously supply charge carriers from the contact zone739 for supporting an external current flow.

FIG. 8A shows a power semiconductor diode 501 with a nominal forwardcurrent greater 1000 mA, e.g., greater 10 A or greater 100 A, based onthe semiconductor device 500 of FIG. 7A. An anode/body well 120 forms anohmic contact with a first load electrode 310 at the front side. Thefirst load electrode 310 forms or is electrically connected to an anodeterminal A. The heavily doped contact zone 739 forms an ohmic contactwith a second load electrode 320 on the back. The second load electrode320 forms or is electrically connected to a cathode terminal K.

FIG. 8B refers to an IGFET 502. As regards details of the semiconductorportion 700, the drift zone 731, the field stop zone 738, the contactzone 739, which is effective as drain, and the vertical dopant profilereference is made to the description of FIGS. 7A to 7B. The IGFET 502includes transistor cells TC, which may be IGFET cells with n-dopedsource zones and with the anode/body well 720 forming body zones of thetransistor cells TC. The body zones separate the source zones from thedrift zone 731, respectively. The source zones may be electricallyconnected or coupled to a first load electrode at the front side. Thefirst load electrode may form or may be electrically connected to asource terminal S.

Gate electrodes of the transistor cells TC may be electrically connectedor coupled to a gate terminal G and may be capacitively coupled to thebody zones through gate dielectrics. Subject to a voltage applied to thegate terminal G, inversion channels are formed in the body zones andprovide an electron flow through the transistor cells TC such that in anon-state of the IGFET 502 electrons enter the drift zone 731 through thetransistor cells TC.

The transistor cells TC may be planar cells with lateral gate structuresarranged outside of the contour of the semiconductor portion 700 ortrench cells with trench gate structures extending from the firstsurface 701 into the semiconductor portion 700. For example, the sourceand body zones of the transistor cells TC may be formed in semiconductormesas separated by the trench gate structures.

FIG. 8C refers to an IGBT 503, for example a PT-IGBT with a p-typecontact zone 739 and with the second load electrode 320 electricallyconnected to a collector terminal C The source and body zones areelectrically connected or coupled to an emitter terminal E. For furtherdetails, reference is made to the description of the power semiconductordiode 501 of FIG. 8A and the IGFET 502 of FIG. 8B.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising: generating crystal lattice defects in ahorizontal surface portion of a semiconductor substrate; forminghydrogen-related donors in the surface portion; obtaining informationabout a cumulative dopant concentration of dopants including thehydrogen-related donors, in the surface portion; determining, based onthe information about the cumulative dopant concentration, a maintemperature profile for dissociating a defined portion of thehydrogen-related donors; and subjecting the semiconductor substrate to amain heat treatment applying the main temperature profile to obtain, inthe surface portion, a final total dopant concentration deviating from atarget dopant concentration by not more than 15%.
 2. The method of claim1, wherein the surface portion contains extrinsic dopants and thecumulative dopant concentration is the sum of an extrinsic net dopantconcentration and a preparatory hydrogen-related donor concentrationafter the forming of the hydrogen-related donors.
 3. The method of claim1, wherein the semiconductor substrate contains extrinsic donors and anextrinsic net dopant concentration is at least 1E13 cm⁻³.
 4. The methodof claim 1, wherein the semiconductor substrate contains extrinsicdonors and an extrinsic net dopant concentration is at most 5E12 cm⁻³.5. The method of claim 1, wherein the semiconductor substrate isintrinsic.
 6. The method of claim 1, wherein forming thehydrogen-related donors comprises a preparatory heat treatment fordiffusing hydrogen into the surface portion.
 7. The method of claim 1,wherein generating the crystal lattice defects comprises irradiating thesemiconductor substrate with protons.
 8. The method of claim 7, furthercomprising: after implanting the protons, thinning the semiconductorsubstrate from a side opposite to the front surface so that a baseportion comprising an end-of-range peak of the proton implant isremoved.
 9. The method of claim 7, wherein forming the hydrogen-relateddonors comprises a preparatory heat treatment for diffusing theimplanted protons into the surface portion.
 10. The method of claim 9,wherein a maximum temperature applied in the preparatory heat treatmentis above 470° C. and at most 510° C.
 11. The method of claim 1, whereina maximum temperature applied in the main heat treatment is above 510°C.
 12. The method of claim 1, wherein at least 50% of a total durationof the main temperature profile is an isothermal process given by aconstant main process temperature and a main process time for which theconstant main process temperature is applied.
 13. The method of claim 1,further comprising: forming anode/body wells in the semiconductorsubstrate, wherein the anode/body wells form first pn junctions withcathode/drain structures, wherein the cathode/drain structures comprisedrift zones in the surface portion, wherein a dopant concentration inthe drift zones is equal to the final total dopant concentration. 14.The method of claim 1, wherein the information about the cumulativedopant concentration comprises a capacitive/voltage measurement acrossat least one of a pn junction and a Schottky contact formed by thesurface portion.
 15. The method of claim 14, wherein a contact probe ispressed against a section of the front surface exposing the surfaceportion.
 16. The method of claim 1, further comprising: forming aninterlayer dielectric at a front side of the semiconductor substratebefore subjecting the semiconductor substrate to the main heattreatment.
 17. The method of claim 1, further comprising: forming aplurality of separated semiconductor dies from the semiconductorsubstrate after subjecting the semiconductor substrate to the main heattreatment.
 18. The method of claim 1, wherein at least 25% of donors inthe semiconductor substrate are hydrogen-related donors after the mainheat treatment.
 19. The method of claim 1, wherein an intrinsic oxygenconcentration in the semiconductor substrate is in a range from 1E17cm⁻³ to 6E17 cm⁻³.
 20. The method of claim 1, wherein a substitutionalcarbon concentration in the semiconductor substrate is in a range from1E14 cm⁻³ to 5E15 cm⁻³.
 21. The method of claim 1, further comprising:after the main heat treatment, implanting protons to form a field stoplayer in the semiconductor substrate.
 22. The method of claim 21,further comprising: subjecting the semiconductor substrate to asupplementary heat treatment which activates the protons to form thefield stop layer, wherein a maximum temperature applied in thesupplementary heat treatment is below 420° C.
 23. The method of claim 1,wherein the semiconductor substrate is subjected to the main heattreatment before forming a first metallization at a front side.